Time-dependent Magnetohydrodynamic Self-similar Extragalactic Jets

• Published in: The Astrophysical journal Vol. 658; no. 2; pp. 794 - 803
• Main Authors: Tsui, K. H, Serbeto, A
• Format: Journal Article
• Language: English
• Published: Chicago, IL IOP Publishing 01-04-2007; University of Chicago Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; MHD; Magnetohydrodynamics; Extragalactic jet; Astrophysical jets; accretion, accretion disks; Accretion disks
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/511739

Extragalactic jets are visualized as dynamic eruptive events modeled by time-dependent magnetohydrodynamic (MHD) equations. The jet structure comes from the temporally self-similar solutions in two-dimensional axisymmetric spherical geometry. The two-dimensional magnetic field is solved in the finite plasma pressure regime, or finite-b regime, and it is described by an equation where plasma pressure plays the role of an eigenvalue. This allows a structure of magnetic lobes in space, among which the polar axis lobe is strongly peaked in intensity and collimated in angular spread compared to the others. For this reason, the polar lobe overwhelms the other lobes, and a jet structure naturally arises in the polar direction. Furthermore, within each magnetic lobe in space, there are small secondary regions with closed two-dimensional field lines embedded along this primary lobe. In these embedded magnetic toroids, plasma pressure and mass density are accordingly much higher. These are termed secondary plasmoids. The magnetic field lines in these secondary plasmoids circle in alternating sequence such that adjacent plasmoids have opposite field lines. In particular, along the polar primary lobe, such periodic plasmoid structure happens to be compatible with radio observations in which islands of high radio intensities are mapped.